Intraepidermal epidermotropic metastatic melanoma: a clinical and histopathological mimicker of melanoma in situ occurring in multiplicity

Abstract

Journal of Cutaneous PathologyIntraepidermal epidermotropic metastatic melanoma: a clinical and histopathological mimicker of melanoma in situ occurring in multiplicityThe distinction between primary melanoma and melanoma metastatic to the skin has major prognostic implications. We report a case of a 67-year-old male with a diagnosis of a superficial spreading melanoma (stage IB) rendered 6 years earlier who presented clinically with an atypical nevus on his left thigh. Histopathological examination showed an intraepidermal melanocytic proliferation that was interpreted as melanoma in situ. Subsequently, 45 additional pigmented macules appeared in crops over a 9-month period. Clinically and dermoscopically, these lesions were extremely polymorphic. Histopathological findings were compatible with melanoma in situ, as each lesion consisted of a wholly intraepidermal proliferation of markedly atypical melanocytes arranged singly and in nests. A complete gastrointestinal study showed multiple pigmented metastatic lesions throughout the stomach and small bowel, which supported a diagnosis of metastatic melanoma with gastrointestinal and epidermotropic skin involvement. Monosomy of chromosome 9 and a BRAF V600E mutation were detected in the primary tumor sample and in macro-dissected secondary lesions. No CDKN2A or CDK4 germline mutations were found. Intraepidermal epidermotropic metastases of melanoma have been rarely described in literature. In this case, histopathology alone was insufficient to distinguish metastatic melanoma from multiple in situ melanomas. The recognition of epidermotropic metastases should be based on the correlation between clinical, dermoscopic, histopathological and molecular findings.

Dermoscopic patterns of melanoma metastases: interobserver consistency and accuracy for metastasis recognition

“…reported a case of melanoma on the scalp and a further 11 skin metastasis mimicking benign melanocytic naevus (with a globular pattern characterized by greyish‐blue globules extending throughout the entire lesion) or primary melanomas (with a multicomponent pattern). Lestre et al . also reported CMMM simulating melanocytic naevi or primary cutaneous melanoma.…”

Comprehensive histopathological comparison of epidermotropic/dermal metastatic melanoma and primary nodular melanoma

“…The occurrence of multiple lesions in the vicinity of the primary melanoma site also provides compelling clinical evidence for metastases. However, when clinicopathological correlation fails to elucidate the primary versus metastatic nature of a lesion, molecular studies may be needed to facilitate more accurate staging …”

“…However, when clinicopathological correlation fails to elucidate the primary versus metastatic nature of a lesion, molecular studies may be needed to facilitate more accurate staging. 15,21 A number of cytomorphological features aid in the distinction between PNM and EDMM. In general, significant pleomorphism favours a diagnosis of PNM, whereas monomorphism favours a diagnosis of EDMM.…”

Multiple acquired pigmented lesions in a patient affected by melanoma

“…In these cases, the term 'epidermotropic metastatic melanoma' is used and the diagnosis can only be made with a thorough evaluation of the medical history, clinical features, dermatoscopy, histology and whenever possible molecular analysis [ 2,3 ] . In these cases, the term 'epidermotropic metastatic melanoma' is used and the diagnosis can only be made with a thorough evaluation of the medical history, clinical features, dermatoscopy, histology and whenever possible molecular analysis [ 2,3 ] .…”