Ishihara Chihiro, Nomura Tadashi, Nakanishi Takaaki, Tsuji Yoriko, Terashi Hiroto
Plastic Surgery, Kobe University Graduate School of Medicine, Kobe, JPN.
Diagnostic Pathology, Kobe University Graduate School of Medicine, Kobe, JPN.
Cureus. 2024 Sep 10;16(9):e69114. doi: 10.7759/cureus.69114. eCollection 2024 Sep.
Bowen's disease (BD), also known as squamous cell carcinoma (SCC) in situ, is a precancerous skin condition that can potentially progress to invasive tumors. Merkel cell carcinoma (MCC) is a rare and aggressive neuroendocrine tumor typically found in sun-exposed areas of elderly Caucasians. The coexistence of BD and MCC is extremely rare, particularly when MCC is located in subcutaneous tissue rather than its typical epidermal or dermal layers. This case report presents an unusual instance of BD coexisting with subcutaneous MCC on the dorsum of the hand in an elderly Japanese male. An 87-year-old Japanese male with over 30 years of sun exposure presented with a progressively enlarging red tumor on the dorsum of his left hand. A biopsy confirmed BD, and the tumor was excised with a 5 mm margin followed by skin grafting. Histopathological examination revealed subcutaneous MCC along with BD, with MCC cells forming small nests in the dermal papillary layer. Immunohistochemistry showed positive staining for synaptophysin and CK20 in a perinuclear dot pattern, confirming the MCC diagnosis. Given the patient's advanced age and the absence of positive surgical margins, a watch-and-wait approach was adopted. The patient has been under close outpatient monitoring, and no recurrence has been observed after six months. This case highlights the rarity of subcutaneous MCC coexisting with BD, with only a few reported cases of such coexistence. The unusual subcutaneous presentation and the presence of multiple micro-nodules instead of large atypical cell clusters suggest an early-stage MCC beneath BD. The pathogenesis of this coexistence remains unclear but raises important questions regarding the relationship between sun exposure and viral factors like Merkel cell polyomavirus (MCPyV), which was not tested in this case. The findings underscore the need for comprehensive diagnostic evaluation when encountering complex or atypical skin lesions. This report emphasizes the rarity of subcutaneous MCC coexisting with BD and underscores the importance of comprehensive diagnostic assessment in unusual cases. Further research is warranted to better understand the underlying mechanisms and to guide optimal management strategies for such rare and challenging presentations.
鲍恩病（BD），也称为原位鳞状细胞癌（SCC），是一种癌前皮肤疾病，有可能发展为侵袭性肿瘤。默克尔细胞癌（MCC）是一种罕见且侵袭性强的神经内分泌肿瘤，通常见于老年白种人暴露于阳光下的部位。BD与MCC并存极为罕见，尤其是当MCC位于皮下组织而非其典型的表皮或真皮层时。本病例报告呈现了一名老年日本男性手部背部BD与皮下MCC并存的不寻常病例。一名有30多年日晒史的87岁日本男性，左手背部出现一个逐渐增大的红色肿瘤。活检确诊为BD，肿瘤以5毫米切缘切除，随后进行植皮。组织病理学检查显示皮下MCC与BD并存，MCC细胞在真皮乳头层形成小巢。免疫组化显示突触素和CK20呈核周点状阳性染色，确诊为MCC。鉴于患者高龄且手术切缘无阳性，采取了观察等待的方法。患者一直在门诊密切监测，六个月后未观察到复发。本病例突出显示了皮下MCC与BD并存的罕见性，仅有少数此类并存病例的报道。不寻常的皮下表现以及存在多个微结节而非大的非典型细胞簇提示BD下方存在早期MCC。这种并存的发病机制尚不清楚，但引发了关于日晒与默克尔细胞多瘤病毒（MCPyV）等病毒因素之间关系的重要问题，本病例未对此进行检测。这些发现强调了遇到复杂或非典型皮肤病变时进行全面诊断评估的必要性。本报告强调了皮下MCC与BD并存的罕见性，并强调了在不寻常病例中进行全面诊断评估的重要性。有必要进一步研究以更好地理解潜在机制，并指导针对此类罕见且具有挑战性表现的最佳管理策略。
