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DOI:10.2214/AJR.04.0796
AJR 2005; 185:1441-1448
© American Roentgen Ray Society

Original Research

MRI of Merkel Cell Carcinoma: Histologic Correlation and Review of the Literature

Suzanne E. Anderson1, Karl T. Beer2, Andrej Banic3, Lynne S. Steinbach4, Matthias Martin1, Esther E. Friedrich2, Edouard Stauffer5, Peter Vock1 and Richard H. Greiner2

1 Department of Diagnostic, Interventional and Pediatric Radiology, University Hospital of Bern, Inselspital, Freiburg Strasse, CH-3010 Bern, Switzerland.
2 Department of Radiation Oncology, University Hospital of Bern, Inselspital, Bern, Switzerland.
3 Department of Plastic and Reconstructive Surgery, University Hospital of Bern, Inselspital, Bern, Switzerland.
4 Department of Radiology, University of California, San Francisco, San Francisco, CA.
5 Department of Pathology, University Hospital of Bern, Inselspital, Bern, Switzerland.

Received May 18, 2004; accepted after revision December 6, 2004.

 
Presented at the 2003 annual meeting of the European Society of Skeletal Radiology, Aarhus, Denmark.

Address correspondence to S. E. Anderson (suzanne.anderson{at}bluewin.ch).


Abstract
Top
 Abstract
Introduction
 Materials and Methods
 Results
 Discussion
 References
 
OBJECTIVE. The objective of this study was to determine the MRI characteristics of Merkel cell carcinoma, with an emphasis on histologic correlation.

MATERIALS AND METHODS. The demographic information about 15 patients from our institution and their MRI examinations were retrospectively reviewed by three musculoskeletal radiologists by consensus for lesion location and intrinsic characteristics. The study group was composed of three women and 12 men who ranged in age from 48 to 87 years, with a mean age of 75 years. Histology results of resected specimens were reviewed in all cases and were correlated with imaging.

RESULTS. MRI showed skin thickening, subcutaneous reticular stranding (n = 9, 60%); multiple anatomically aligned subcutaneous soft-tissue masses, representing lymphatic tumor nodules (n = 5, 33%); lymph node enlargement with fine, compressed, retained fatty tissue (n = 5, 33%); nodal necrosis (n = 1); and perifascial and intramuscular metastases (n = 2). Histology confirmed the lymphatic nature of the soft-tissue Merkel cell tumors.

CONCLUSION. Patients with Merkel cell tumors may present at imaging with subcutaneous lymphatic reticular stranding, multiple subcutaneous masses, and lymph node metastases. Often there is massive lymph node enlargement with fine, compressed, retained fatty tissue.


Introduction
Top
 Abstract
 Introduction
Materials and Methods
 Results
 Discussion
 References
 
Merkel cell carcinoma is a rare dermal malignant tumor with neuroendocrine elements. It has received limited coverage in the radiology literature with small case series and case reports often focused on metastatic disease and the role of imaging largely limited to staging. This is probably because it is a skin tumor usually detected by clinical examination and the final diagnosis is made by histopathology with light and electron microscopy and immunohistochemistry.

To our knowledge, this is the first series with a relatively large number of patients (15 patients) with Merkel cell carcinoma to evaluate the primary site in addition to metastatic foci on MRI. This series is also interesting because it is slightly atypical given that the head and neck region was the primary site in only eight of the 15 patients and that the unique MRI appearances are correlated with histology. We hope to increase the awareness of musculoskeletal radiologists to this dangerous early lymphatic metastasizing dermal malignant tumor to allow improved diagnosis and appropriate therapy.


Materials and Methods
Top
 Abstract
 Introduction
 Materials and Methods
Results
 Discussion
 References
 
Patients
This is a retrospective study. Written informed consent was obtained from all patients before imaging, and consent was obtained from the local governmental ethics committee as part of the routine radiooncology service requirement to allow open review and publication of all medical details. The MRI findings of 15 patients who presented to our institution between May 20, 1994, and March 12, 2003, with histologically proven Merkel cell carcinomas were evaluated. The patient list was generated from retrospective chart review of irradiated patients who had undergone imaging either for tumor staging of local lymphatic metastases or any other metastases or for unusual clinical symptoms that may be caused by tumor. Imaging had been performed to offer an appropriate radiation therapy portal to maximize the therapy. The study group was composed of three women and 12 men who ranged in age from 48 to 87 years, with a mean age of 75 years.

The tumor sites were the hip and leg region in three patients, shoulder and arm region in four patients, and head and neck region in eight patients. The patients were referred within 1 month after incomplete intralesional surgery for imaging and appropriate therapy. The tumor size ranged from 1 cm to 17 x 11 cm.

Four patients had additional histories of a second malignant tumor: three patients had malignant prostate tumors and one patient who had undergone immunosuppressive therapy after renal transplantation had multiple malignant skin cancers. One patient had a diagnosis of polymyalgia rheumatica and was on long-term steroid therapy.



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  		Fig. 1A —MR images of typical patient with Merkel cell carcinoma show one unique imaging finding of Merkel cell carcinoma: positive anatomic alignment of subcutaneous lymphatic tumor nodules. Patient is 63-year-old man with primary tumor in skin of right popliteal fossa. Axial T1-weighted image (TR/TE, 480/14) shows multiple skin and subcutaneous metastases in anterior proximal thigh (black arrows). Because these are lymphatic metastases and are small, small regions of fat remain between tumor nodules (white arrow).

 



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  		Fig. 1B —MR images of typical patient with Merkel cell carcinoma show one unique imaging finding of Merkel cell carcinoma: positive anatomic alignment of subcutaneous lymphatic tumor nodules. Patient is 63-year-old man with primary tumor in skin of right popliteal fossa. Corresponding axial STIR image (4,800/60; inversion time, 180 msec) shows high signal intensity of skin and subcutaneous lymphatic metastases (small arrows), an example of positive anatomic alignment of subcutaneous lymphatic tumor nodules. Marked reticular stranding in subcutaneous fat is also seen. Histologically these two findings were shown to represent lymphangitis carcinomatosa. Lymph node metastases (large arrow) are seen adjacent to proximal superficial femoral artery.

 



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  		Fig. 1C —MR images of typical patient with Merkel cell carcinoma show one unique imaging finding of Merkel cell carcinoma: positive anatomic alignment of subcutaneous lymphatic tumor nodules. Patient is 63-year-old man with primary tumor in skin of right popliteal fossa. Axial STIR image (4,800/60; inversion time, 180 msec), obtained inferior in relation to A and B, shows perifascial intramuscular metastasis (arrow) and extensive reticular stranding in anterior and medial subcutaneous fat of thigh.

 



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  		Fig. 1D —MR images of typical patient with Merkel cell carcinoma show one unique imaging finding of Merkel cell carcinoma: positive anatomic alignment of subcutaneous lymphatic tumor nodules. Patient is 63-year-old man with primary tumor in skin of right popliteal fossa. Contrast-enhanced T1-weighted fat-saturated image (684/14) shows diffuse contrast enhancement within subcutaneous and intramuscular metastases (arrow).

 
Imaging
The regions reviewed with MRI were the thigh (n = 5); pelvis and abdomen (n = 2); brain, base of skull, and head and neck (n = 5); axilla, suprascapular and shoulder region (n = 2); forearm (n = 1); and anterior chest wall (n = 1). The anatomic area imaged on MRI included the primary tumor and, in addition, an expanded MRI field for lymphatic staging of adjacent lymph nodes that would be appropriate to cover in a radiation therapy treatment portal and for any odd clinical symptoms that may be explained by tumor involvement.

MRI was performed on a 1.5-T scanner (Vision, Siemens Medical Solutions). Sequences for peripheral tumors included STIR (TR range/TE range, 5,200-5,300/60-70; inversion time, 180 msec), T1 weighting (480-540/12-14), T2 weighting (3,200-3,400/70-85), and T1 weighting after contrast administration with fat saturation in the axial plane (524-684/12-14). Sequences for the face and the head and neck region included STIR (4,900-5000/30-40; inversion time, 120 msec) in the coronal plane, T1 weighting (534-560/12-14) and T2 weighting (4,600-4,900/70-80) in the axial plane, and T1 weighting after contrast administration with fat saturation in the coronal (600-748/12-14) and axial (600-673/12-14) planes.



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  		Fig. 1E —MR images of typical patient with Merkel cell carcinoma show one unique imaging finding of Merkel cell carcinoma: positive anatomic alignment of subcutaneous lymphatic tumor nodules. Patient is 63-year-old man with primary tumor in skin of right popliteal fossa. Photomicrograph of histology section shows skin surface (small arrow) and tumor mass (large arrow) within subcutaneous fat. (H and E, x2.5)

 



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  		Fig. 1F —MR images of typical patient with Merkel cell carcinoma show one unique imaging finding of Merkel cell carcinoma: positive anatomic alignment of subcutaneous lymphatic tumor nodules. Patient is 63-year-old man with primary tumor in skin of right popliteal fossa. Enlargement of photomicrograph shown in E reveals subcutaneous tumor mass is composed of dense small blue cells with hyperchromatic nuclei, minimal cytoplasm, and frequent mitoses. These histologic features may account for slight increased signal intensity on T1 weighting within small subcutaneous nodules. (H and E, x10)

 



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  		Fig. 1G —MR images of typical patient with Merkel cell carcinoma show one unique imaging finding of Merkel cell carcinoma: positive anatomic alignment of subcutaneous lymphatic tumor nodules. Patient is 63-year-old man with primary tumor in skin of right popliteal fossa. Photomicrograph of histology section shows lymphatic tumor invasion (arrows) and dilated lymphatic vessels (arrowhead), which correspond to reticular stranding and subcutaneous nodules on MRI. (H and E, x5)

 
Contrast material was administered as part of the tumor protocol for tumor necrosis to define cystic regions and to optimize the biopsy site. Sequences for imaging the axilla and supraclavicular region and anterior chest wall included STIR in the coronal and axial planes, T1 weighting in the axial and sagittal planes, and T2 weighting in the axial plane. All patients had additional imaging series with CT (n = 39 studies), radiography (n = 54), sonography (n = 6), somatostatin scintigraphy (n = 1), or PET (n = 2); however, the primary aim of the study was to review the MRI findings and correlate those finding with histology results to allow an improved understanding of this tumor. Follow-up imaging was not performed on a routine standardized basis because the patients were referred to the tertiary institute for restaging and therapy and were then referred back to the primary center.

Evaluation of Imaging and Pathology
The presence of skin and subcutaneous nodules (1-1.5 cm) and of subcutaneous reticular stranding and the frequency of local tumor migration at the time of MRI in patients with large lymph node masses with retained compressed internodal fat, perifascial and intramuscular metastases, tumor necrosis, and lymph node and distant metastases were reviewed by three radiologists by consensus (two senior and one junior in training). The evaluations were not blinded, and no special data forms were used. Features included site, size, morphology, and MR signal characteristics of the tumor and metastases (distant lymph nodes, lung, and bone). MRI was then compared with histomorphology and immunohistochemistry of the excised specimens of all patients. The site, size, and presence of tumor necrosis or invasion of local lymphatic structures and sites of metastatic disease were investigated. Also the cellular density and histologic structure of the tumors were reviewed for correlation with the MRI signal intensities. The listed features were recorded by the histopathologist, and a radiologist correlated those findings with the MRI findings later during separate sessions. At later sessions, the histology was reviewed under the microscope and the MRI findings were then discussed on a case-by-case basis. Direct correlation of MRI with histopathology is part of the institution's tumor pathology review and is possible due to accurate demarcation for orientation of all surgical specimens.


Results
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 Abstract
 Introduction
 Materials and Methods
 Results
Discussion
 References
 
Of the 15 patients referred to undergo imaging for staging, MRI showed signs of regional tumor migration including small lymph nodes with characteristics of metastatic disease in 14. Regional tumor migration is defined as spread to local lymphatics and lymph node drainage areas—for example, from the upper arm to axillary lymph nodes. From this group of 14, nine patients had subcutaneous reticular stranding; five patients had skin and subcutaneous tumor nodules that were commonly aligned in a row or column in close approximation to each other (Figs. 1A, 1B, 1C, 1D, 1E, 1F, and 1G); and five patients had hematogenous parenchymal metastases, two in the lung and three in bone (Table 1).


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  		TABLE 1 : MRI Findings in 15 Cases of Merkel Cell Carcinoma

 

The skin and subcutaneous lesions measured 1-1.5 cm and were slightly higher in signal intensity than muscle on T1-weighted images (n = 5, 33%) and occurred in two patients with gluteal and peripheral lesions, one patient with lesions in the facial region, and two patients with lesions in the axilla and shoulder region. The skin, subcutaneous masses, and reticular stranding histologically were found to be caused by lymphangitis carcinomatosa and soft-tissue lymphatic metastases.

Perifascial muscular and intramuscular tumor metastases (Fig. 1D) were present in two patients. The early evidence of intramuscular tumor shows high-grade invasive and aggressive tumor cells.

Five patients had large lymph node metastases, ranging from 2 x 2 cm to 20 x 7 x 12 cm, in the axilla in two patients, supraclavicular and mediastinal nodes in one patient, and inguinal nodes in two patients. Fine, compressed intranodal fat was retained between the nodal masses (Figs. 2A and 2B). The MRI findings were confirmed by histologic examination.



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  		Fig. 2A —Example of large lymph node metastases with compressed retained fatty tissue in 86-year-old man with primary tumor site in skin of axilla. Axial T1-weighted image (TR/TE, 534/12) of right axilla shows large lymph node metastatic mass with fine, compressed, retained fatty tissue (arrows).

 


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  		Fig. 2B —Example of large lymph node metastases with compressed retained fatty tissue in 86-year-old man with primary tumor site in skin of axilla. Sagittal T1-weighted image (534/12) of axillary lymph nodal metastases, measuring 20 x 7 x 12 cm, shows subtle fine, compressed, retained fatty tissue of fat signal intensity (arrows).

 
When the main tumor mass (either primary or metastatic) was subcutaneous and 1-1.5 cm, it was isointense to slightly hyperintense in signal intensity in relation to peripheral muscle on T1-weighted images, had increased signal intensity on T2-weighted and STIR images, and showed diffuse contrast enhancement after the administration of gadolinium. The signal intensity was homogeneous in all sequences for tumors smaller than 2 cm, but in one patient after biopsy there was inhomogeneous signal intensity. Larger masses had a more subtle inhomogeneous signal pattern on T2-weighted and STIR images. Tumor necrosis (Fig. 2C) was shown in one patient. Surgery had been performed in 13 of 15 patients at other institutions.



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  		Fig. 2C —Example of large lymph node metastases with compressed retained fatty tissue in 86-year-old man with primary tumor site in skin of axilla. Axial T1-weighted contrast-enhanced fat-saturated image (524/12) shows evidence of tumor necrosis (arrow).

 

Discussion
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 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
References
 
The Merkel cell was initially described in 1875 by Friedrich Merkel [1] as an epidermal nondendritic, nonkeratinocyte cell, which he called a "tactile cell." In 1978, Tang and Toker [2] first suggested that skin tumors might arise from Merkel cells. Initially a Merkel cell tumor was handled as a local malignant tumor, but nowadays an increasing number of published reports describe marked aggressive behavior with rapid growth [3, 4] and early lymphatic and hematogenous dissemination.

There are only a few imaging reports on Merkel cell carcinoma. Most concentrate on the use of nuclear medicine with somatostatin (octreotide) [5-7], PET [8, 9], and CT [3, 10, 11] for staging metastatic disease. MRI appearances are described in small series and several case reports, all of which support the usefulness of MRI in evaluating this tumor. In one case report, the authors describe the appearance of a primary peripheral lower limb soft-tissue tumor [12]. Distant bony metastatic disease to the spine and pelvis associated with soft-tissue extension and epidural involvement has been described [13], and both intra- and extradural spinal metastatic diseases have been described in other case reports [14, 15]. Other imaging techniques have been reported to be useful in investigating bone metastases, which appear to be rare with only several case reports describing the disease as evident, usually within 1 year of presentation [13, 16-18].

Case reports on primary disease to the sinonasal region [19], orbit [20], and abdominal wall [21] also support the use of MRI in investigating this tumor. Large lesions are described as being inhomogeneous in signal intensity on both T1- and T2-weighted images. Focal central increased signal intensity on T2-weighted images within large lesions has been described as being associated with histologically proven central necrosis and hemorrhage [21]. One educational article depicts all stages of the disease with a variety of imaging techniques for largely metastatic disease [22]. The authors of that article state that to date clinical data to define the role of imaging are insufficient and that there is no optimal imaging algorithm. Lymphatic mapping using radionuclide lymphoscintigraphy and sentinel lymph node biopsy has been advocated, particularly for tumors in the head and neck region [22, 23]. With the advent and increasing use of MR lymphangiography [24] and ultrasmall superparamagnetic iron oxide particles, this technique may be useful in investigating for local and nearby lymphatic spread of tumor.

Merkel cell carcinoma is a rare malignant cutaneous neoplasm. On the basis of demographic data for the United States, 470 new cases per year are estimated to occur compared with 31,000 new cases of malignant melanoma. There is usually a male predominance, as was the case in our series, and the average age at presentation is 69 years. Patients usually present with a reddish or bluish intracutaneous nontender firm mass in a sun-exposed area. The cause remains unknown; however, it has been linked to sun exposure by its anatomic and geographic distribution [3]. Another possible cause is impaired immune status, related to iatrogenic immunosuppression, HIV infection [25, 26], or neoplasia. Most patients, 70-80% [3], present with localized skin disease; however, this tumor is known to metastasize widely, with a reported frequency of 36% [10]. At presentation, up to 30% of patients have regional lymph node involvement and 1-4% have hematogenous metastases [3]. In decreasing order of frequency, common secondary sites include skin, lymph nodes, liver, bones, and brain [3]. Distant rare visceral metastases have been described in the prostate and bladder [27], heart [28], stomach [29], and pancreas [30].

There is no accepted clinical staging system for Merkel cell carcinoma; however, several investigators [3] have adopted a system proposed by Yiengpruksawan et al. [31], with stage I being localized skin disease (stage IA, < 2 cm; stage IB, > 2 cm); stage II, regional lymph node disease; and stage III, metastatic disease. The overall recurrence rate ranges from 55% to 80%, with the majority of recurrences occurring within the first 6-12 months and most commonly occurring locally or within lymph nodes. Therefore, strong clinical and imaging surveillance is recommended.

Our study determined that MRI is useful in the investigation of Merkel cell tumor because it shows the location and extent of tumor and local regional lymph node involvement, and we found MRI helpful for planning target volume radiation therapy and documenting tumor characteristics before and after therapy to assess tumor response to therapy.



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  		Fig. 2D —Example of large lymph node metastases with compressed retained fatty tissue in 86-year-old man with primary tumor site in skin of axilla. Photomicrograph of histology section of tumor mass with central necrosis (asterisk) corresponding to tumor necrosis shown in C. Infiltration of adjacent fat tissue (arrow) is noted. (H and E, x2.5)

 
In a CT series, Gollub et al. [10] speculated early tumor spread by lymphatics is suggested by the multiple subcutaneous satellite lesions. In a case report, Dunlop et al. [21] described the presence of two subcutaneous satellite lesions, one near to the primary abdominal wall tumor and one distant in the inguinal region. In our study, we correlated MRI findings with the histomorphology and immunohistochemistry results. We could confirm that reticular stranding and the presence of subcutaneous masses, representing subcutaneous satellite nodules, are due to lymphatic tumor spread with lymphangitis carcinomatosa and lymphatic metastases. Peritumoral lymphatic spread has been described previously in the pathology literature [32, 33]. The histologic correlation also confirmed that large regional lymph node metastases have fine, compressed, retained fatty tissue or have necrotic areas.



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  		Fig. 3A —77-year-old man with primary tumor site in periorbital region. Axial T1-weighted image (TR/TE, 750/25) before radiation therapy shows sternum (arrow).

 



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  		Fig. 3B —77-year-old man with primary tumor site in periorbital region. Corresponding axial T1-weighted contrast-enhanced fat-saturated image (601/12) shows large exophytic soft-tissue component (arrows).

 



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  		Fig. 3C —77-year-old man with primary tumor site in periorbital region. Axial T1-weighted image (750/25) 1 month after radiation therapy (total dose, 45 Gy) shows excellent response with marked reduction in tumor bulk of sternal disease (arrow). In our series after local radiation therapy, there was typically marked reduction of tumor bulk or excellent tumor response.

 



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  		Fig. 3D —77-year-old man with primary tumor site in periorbital region. Corresponding axial T1-weighted contrast-enhanced fat-saturated image (159/48) shows excellent response to radiation therapy with marked reduction of exophytic soft-tissue component of sternal tumor (arrow).

 
This tumor arises in the dermis but extends frequently into subcutaneous fat. The overlying epidermis is commonly intact. Clinically, the subcutaneous manifestations may be palpable as small nodules with signs of surrounding skin hyperemia. Histologically, the tumor is composed of dense small blue cells with hyperchromatic nuclei, minimal cytoplasm, and frequent mitoses. These histologic features may account for subtle increased signal intensity within small tumor nodules on T1-weighted imaging and for the clear visibility against a background of subcutaneous fat.

Increased signal intensity on T1-weighted imaging has been described in several soft-tissue tumors, such as clear cell sarcoma, with melanocytic differentiation being the probable cause for the signal intensity [34], which usually occurs adjacent to tendons or fascia; in melanoma and its metastases; in synovial sarcoma, particularly if cystic in nature with increased T1 weighting due to hemorrhage [35]; and in neural tumors [36]. However, the signal characteristics of the primary and satellite metastases are not characteristic of a specific tumor, as has been noted in a previous case report [21]. Multiple nodular subcutaneous metastases have been also described in association with metastatic melanoma [37] and with extraosseous involvement of multiple myeloma [38]; however, they are not associated with an anatomic alignment in their distribution.

The variable subtle mosaic signal intensity of metastatic lesions larger than 1.5 cm is accounted for by the presence of fine stromal septa. There are three main histologic subsets: intermediate, small cell, and trabecular, although usually tumors are a mixture of these cell types. The small cell variant, with irregular hyperchromatic cells showing frequently a crush artifact and nuclear molding, is similar to the bronchial small cell carcinoma and must be differentiated from this and melanoma with immunohistochemistry (S-100 protein; creatine kinase, CK20 and CK7; thyroid transcriptase factor 1) [3, 4] and must be differentiated from cutaneous lymphoma with electronic microscopy [39] or immunohistochemistry (chromogranin A).

The Merkel cell tumor subcutaneous metastases and subcutaneous masses in a row distribution were visible on both MRI and CT; however, in our series MRI improved the differentiation of the metastases. In addition, intramuscular metastases and malignant perifascial tumors were better defined on MRI, being either not visible or difficult to diagnose on CT. The difficulty in diagnosing malignant perifascial tumor with CT has been commented on by other investigators [40]. In our experience, some clinically silent subcutaneous metastases can be staged with MRI, which can alter the radiation therapy target volume. Therefore, we recommend close inspection of all subcutaneous regions imaged.

Small cell lung soft-tissue metastasis, lymphoma, and melanoma remain the main radiologic differential diagnoses for Merkel cell carcinoma. The other radiologic differential diagnosis is the very rare epithelioid sarcoma, which also may present with multiple soft-tissue nodules of the skin and subcutaneous regions with often aggressive and early regional lymph node disease [41].

Initially patients with Merkel cell carcinoma were thought to have a good prognosis. However, a recent report in the literature found this tumor is highly aggressive and comparable to small cell lung cancer and melanoma [3]. Previously, wide local surgery with radical regional lymphadenopathy was recommended due to the aggressive nature of this tumor. On the basis of our experiences and the aggressiveness of the Merkel cell tumor, we recommend initial limited local surgery (e.g., biopsy) followed by extended local and regional external radiation therapy, because this tumor is radiosensitive [42] (Figs. 3A, 3B, 3C, and 3D). Inoperable tumors may be treated by radiation therapy alone because the outcomes are similar to those with classic wide surgical resection [43]; however, some authors suggest further investigations [44]. Although the exact role of chemotherapy has not yet been evaluated, currently it is frequently used in metastatic disease. Newer alternative treatments, such as the use of topically applied immunomodulating creams [45] and radiolabeled somatostatin analogue targeted radiation therapy [46], have been reported in case reports to be successful.

We acknowledge the limitations of our study with its retrospective nature and small patient population. However, to date this is the first and largest series of reported Merkel cell carcinoma with MRI and histologic correlation and an unusual distribution of tumors. Our series of Merkel cell carcinomas is a little unusual given that head and neck distribution is typical in other series; therefore, there was a need to document these cases. These lesions may be more common in the peripheral limbs than previously known and may remain unrecognized or may be misinterpreted.

In conclusion, malignant Merkel cell carcinoma of the skin may present to the musculoskeletal radiologist on MRI as a mass with unusual imaging findings of multiple subcutaneous lymphatic metastases in a row formation, reticular stranding with lymphangitis carcinomatosa, and large lymph node metastases with fine, compressed, retained fatty tissue. Awareness of these imaging findings may allow inclusion of the rare Merkel cell carcinoma in the radiologic differential diagnosis and discussion supporting radiation therapy for treatment as opposed to recurrent surgery. It is recommended that MRI be used for staging and that regional lymph nodes and adjacent soft-tissue regions be included to determine the presence of lymphatic tumor spread. We hope this article may draw some attention to this very dangerous early lymphatic metastasizing dermal malignant tumor.


References
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
 References
 

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