Metastatic Mimics of Primary Cutaneous Lesions: Averting Diagnostic Pitfalls With Significant Repercussions

Abstract

Cutaneous metastases by solid malignancies often signify advanced disease and portend severely limited survival. Appropriate diagnosis of these lesions is particularly hampered when they closely resemble primary cutaneous tumors. In this article, we present two diagnostically challenging cases of metastatic lesions to the scalp bearing striking histologic resemblance to primary cutaneous neoplasms. One case of a metastatic urothelial carcinoma showed epidermotropism as well as histologic and immunohistochemical features virtually indistinguishable from those of a poorly differentiated squamous cell carcinoma. Next generation sequencing was performed on both the primary urothelial carcinoma and scalp malignancy revealing an identical BRAF p. S467L somatic mutation, confirming the diagnosis. Another case of metastatic renal cell carcinoma showed clinical and histomorphologic features highly reminiscent of a pyogenic granuloma. These cases demonstrate the potential of metastatic lesions to assume a myriad array of innocuous disguises and underscore the vigilance required to avoid misdiagnosis. In addition, we highlight the emerging role of molecular strategies in resolving these problematic cases.

Independent primary cutaneous and mammary apocrine carcinomas with neuroendocrine differentiation: Report of a case and literature review

“…Given the importance of resolving this quandary, from treatment and prognostic perspectives, molecular studies were undertaken. In contrast to findings in an earlier report, 27 in which NGS was used to identify identical pathogenic somatic mutations in a urothelial carcinoma of the kidney and a tumor on the scalp, disclosing the metastatic nature of the latter, NGS results proved inconclusive in our case. NGS also failed to identify a putative germline pathogenic mutation predisposing to the development of these unusual ACs at different sites.…”

The complexity of cancer immunotherapy illustrated through skin tumors

“…Dermatopathologists are routinely required to identify primary skin tumors rather than dermal metastases, at any location, making the use of genetic and immunohistochemical markers essential. [4][5][6] It is crucial to perform a correct and accurate diagnosis of skin tumor typology before starting any treatment, especially IT. The structural and functional complexity of the skin results in greater diversity of neoplastic lesions than in other tissues, therefore requiring epithelial, neural, endocrine, or lymphoid markers to reveal the original linage of the tumoral cells.…”