Therapy-related myeloid neoplasms with different latencies: a detailed clinicopathologic analysis.

Therapy-related myeloid neoplasm (t-MN) arising in patients with prior cytotoxic treatments is considered a distinct entity due to its unfavorable prognosis. Latencies between the initial cytotoxic therapy and the occurrence of t-MNs vary but usually fall between 1 and 10 years. t-MNs with unusually short or long latencies are not well characterized. It is unclear if they are biologically similar to the ones with ordinary latencies and should be kept in the t-MN entity. We compiled a cohort of t-MN cases including short (<1 year), ordinary (1-10 years), and extended (>10 years) latencies from two tertiary medical centers. Both the t-MNs with ordinary and extended latencies showed high likelihood of high-risk genetic abnormalities and demonstrated no significant survival differences. But the t-MNs with extended latencies were more likely associated with history of multiple cancers (p = 0.007) and were younger at the time of cytotoxic treatments (p < 0.001) when compared to the t-MNs with ordinary latencies. The t-MN with short latencies appears to be a very rare and highly heterogeneous group. In summary, the genetic composition appears similar in the t-MNs with ordinary and extended latencies. However, the association between the t-MN with extended latencies and history of multiple cancers raises a possibility that cancer predisposition may contribute to the accumulation of genetic abnormalities in these patients. Investigation into potential germline mutations in the t-MN patients with extended latencies may provide important information for related family members.

Morphologic Spectrum of Rhabdomyomatous Mesenchymal Hamartomas (Striated Muscle Hamartomas) in Pediatric Dermatopathology.

BACKGROUND: Rhabdomyomatous mesenchymal hamartomas (RMHs), also termed striated muscle hamartomas, are rare benign tumors of skin and subcutis, which mostly occur at birth with a predilection for the head and neck. Simple surgical excision is the treatment modality of choice with excellent prognosis. OBJECTIVE: To review the spectrum of the different clinical and pathologic features of RMHs in pediatric patients and recognize their characteristics to avoid confusion with other lesions in their list of differential diagnosis. METHODS: Six cases of RMH diagnosed at our institution from 2009 to 2021 were retrieved from our files and reviewed retrospectively after anonymization by an honest broker. This review is IRB-approved by the University of Pittsburgh School of Medicine, study STUDY19080192. RESULTS: The patients' age ranged from 6 days to 8 years, with a female predominance (2:1). In all cases, the lesion was present at birth. All lesions, except for 2, occurred in the head and neck regions. One patient had multiple additional small nodules in the face, whereas all others presented with solitary RMHs. The size of the lesions varied, and their composition included bundles of skeletal muscle (the landmark finding) associated with variable amounts of adipose, fibrous, vascular, nerve, and adnexal structures. CONCLUSIONS: RMH is a benign hamartomatous lesion with a variable phenotypic spectrum. RMHs predominate in the head and neck. Familiarity with these lesions, including their presentation in less frequent anatomical sites, is important to avoid diagnostic misinterpretations and potential overtreatment. This study represents one of the largest series of RMHs in the literature, including an unusual case in a perianal location.