Late Metastases from a Thin Primary Cutaneous Malignant Melanoma

Cutaneous malignant melanoma is the third most common type of skin cancer, and its incidence has been rising. Its mortality rate is considerable, due to an aggressive phenotype and great ability of dissemination, mainly in the first years of follow- -up. Late recurrences, those presenting more than 10 years after diagnosis, are rare. The main prognostic factor of cutaneous malignant melanoma is tumor thickness, which also guides management. Thin tumors often have a good prognosis. We report a case of a 66-year-old woman with a history of excision of a thin primary cutaneous malignant melanoma of the dorsum, presenting 16 years later with an unexpected, rapidly progressing and lethal recurrence.

Pathological review of primary cutaneous malignant melanoma by a specialist skin cancer multidisciplinary team improves patient care in the UK

AimsThe National Institute for Health and Care Excellence advocated the development of specialist skin cancer multidisciplinary teams (SSMDTs) for the management of higher risk invasive skin cancers in the UK. The interobserver variability in the histopathological assessment of primary cutaneous malignant melanoma (PCMM) is well recognised.MethodsWe evaluated the discordance rates in the assessment of the histopathological criteria of PCMM based on the eighth American Joint Committee on Cancer (AJCC) melanoma staging system and subsequent change in prognosis and management following pathology review by an SSMDT.Results353 cases of PCMM were referred to our SSMDT between April 2015 and May 2016. Cases in which there was a discrepancy in one or more histological parameters following expert review were collected retrospectively. Of 341 eligible cases, there were 94 (27.6%) in which there was an alteration in any parameter. There was interobserver agreement in final diagnosis in 96.8%, Breslow thickness in 86.8%, ulceration in 98.2%, microsatellites in 98.5%, tumour mitotic rate in 88.9%, histological subtype in 92.4%, growth phase in 98.5%, angiolymphatic invasion in 97.7%, perineural invasion in 98.8%, regression in 95.3% and tumour-infiltrating lymphocytes in 95.0%. A corresponding change in AJCC stage occurred in 23 cases (6.7%), with a resulting change in clinical management in 10 cases (2.9%).ConclusionsDisagreements in the pathological assessment of PCMM can have significant clinical implications for a small number of patients. Our findings highlight the value of the SSMDT for high-quality care of patients with melanoma in the UK.

Undifferentiated Sarcoma as Intermediate Step in Rhabdomyosarcomatous Transformation of a Metastatic Malignant Melanoma Resistant to Anti-BRAF Therapy: A Phenomenon Associated With Significant Diagnostic and Therapeutic Pitfalls

Undifferentiated sarcoma has been hypothesized as an intermediate step in the progression of malignant melanoma to rhabdomyosarcoma. The current report describes a new case of rhabdomyosarcomatous transformation in a malignant melanoma and documents the temporal progression of the malignant melanoma to rhabdomyosarcoma in different metastatic sites via undifferentiated sarcoma. A 65-year-old female with a past medical history of malignant melanoma presented with a new lung mass. A core biopsy revealed a malignant spindle cell neoplasm that was negative for all melanocytic markers, suggesting the possibility of a primary pulmonary sarcomatoid carcinoma or sarcoma. The subsequent lobectomy demonstrated an undifferentiated spindle cell neoplasm with areas of rhabdomyoblastic differentiation. Review of the skin lesion and lymph nodes confirmed the diagnosis of the primary cutaneous malignant melanoma, but also revealed that the nodal metastases had largely transformed into an undifferentiated sarcoma with similar morphology as the spindle cell neoplasm in the lung. Molecular studies demonstrated an identical BRAFV600E mutation in both the primary malignant melanoma and the lung tumor. Interestingly, the metastatic malignant melanoma with rhabdomyosarcomatous transformation was the single metastasis resistant to anti-BRAF therapy, whereas other metastases displayed dramatic clinical responses. The case report provides further supportive evidence that undifferentiated sarcoma is an intermediate step in the progression of malignant melanoma to rhabdomyosarcoma. Pathologists should be aware of this phenomenon as proper documentation of an undifferentiated sarcoma or newly acquired phenotypic variations in a malignant melanoma could considerably improve diagnostic accuracy and therapeutic management of subsequent recurrences.