Merkel cell carcinoma arising in association with cutaneous T‐cell lymphoma: A potential diagnostic pitfall

Abstract

Merkel cell carcinoma (MCC) is a rare, aggressive cutaneous neuroendocrine carcinoma with increased prevalence in patients with immunosuppression or B‐cell neoplasms. To the best of our knowledge, an association with cutaneous T‐cell lymphoma (CTCL) has not been previously described. In this report, we present two cases of MCC arising in the setting of CTCL. The first case was a female during her 70s with previously diagnosed stage IVA1 Sezary syndrome. Biopsy of a scaly patch showed two distinct abnormal cell populations. The first population consisted of hyperchromatic dermal and epidermotropic lymphocytes, expressing CD3 and CD4 with diminished CD7. The second population consisted of intraepidermal clusters of larger atypical cells that expressed synaptophysin, neurofilament, CK20, and Merkel cell polyomavirus transcript. The combination of findings was consistent with intraepidermal MCC in a background of CTCL. Excision showed residual intraepidermal MCC without dermal involvement. The second case was a male during his 50s with a longstanding history of mycosis fungoides, who presented with a new lesion on his right thigh. Biopsy and excision showed dermal MCC without secondary involvement by CTCL. Our cases show that MCC may rarely occur in the setting of T‐cell lymphoma, and that intraepidermal MCC may mimic epidermotropic T‐cells.

Merkel cell carcinoma in situ: A systematic review of prognosis and management

“…However, it is difficult to interpret the significance MCPyV positivity in the context of a limited number of studies testing for the virus, in the pathogenesis of MCCis. 32,33 The rarity of MCCis confirmed by this systematic review precludes any high-level evidence regarding management or prognosis. This review found that among the cases for which management was reported, all except one patient underwent wide local excision and three also underwent sentinel lymph node biopsy.…”

“…Eight of the MCCis cases were tested for MCPyV, with 2 returning a positive result. However, it is difficult to interpret the significance MCPyV positivity in the context of a limited number of studies testing for the virus, in the pathogenesis of MCCis 32,33 …”

Pigmented intraepithelial Merkel cell carcinoma mimicking melanoma in situ

“…Lesions of intraepidermal MCC/MCCIS without documented invasion are exceedingly rare. A search of the PubMed‐indexed, English‐language literature yielded only 17 MCCIS cases documented to date 11–25 . Significant data compiled from these publications, including our case, are summarized in Table 1.…”

“…A search of the PubMed-indexed, English-language literature yielded only 17 MCCIS cases documented to date. [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] Significant data compiled from these publications, including our case, are summarized in Table 1. Two previously reported MCCIS cases were excluded because one case that initially presented solely as MCCIS subsequently developed a deep invasive component, 3 and the second case presented with focal evidence of microinvasion into the papillary dermis.…”

CK20/CK7 double‐negative Merkel cell carcinoma in situ: A case report

“…In most cases of MCC, the tumor is situated within the dermis, or less commonly within the epidermis and dermis; the rate of MCC with an epidermal component is 8%–14% of cases. MCC can also occur in association with other neoplasms and hyperplastic lesions, including squamous cell carcinoma, basal cell carcinoma, cutaneous T‐cell lymphoma, actinic keratosis, poroma, Bowen disease, epidermal cyst, and trichilemmal cyst 7–12 . Cases of MCC with restricted intraepidermal involvement, or Merkel cell carcinoma in situ (MCCIS), are significantly rarer.…”