Proposal for reclassifying MUMP as complex mesothelial tumor of the tunica vaginalis
Well-differentiated papillary mesothelial tumor and malignant mesothelioma are well-recognized entities arising from the testis tunica vaginalis. Mesothelioma of uncertain malignant potential (MUMP) is also a mesothelial lesion seen exclusively at this site. MUMP is reminiscent of well-differentiated papillary mesothelial tumor (WDPMT) yet demonstrates variable proportions of the tumor composed of more complex architectural patterns that could be confused with invasion. MUMP was first described in 2010, and 11 cases had been reported since that time. The authors described 19 additional patients with MUMP who had not yet been reported on and who underwent hydrocelectomy, excision, or orchiectomy. Novel morphologic patterns, in addition to those in the 2010 series, included spindle cells, keloidal-type collagen, and multicystic architecture lined by bland mesothelial cells. Clinical follow-up of nine patients for more than one year (1.5–22.5 years; median, 4.5 years) revealed no evidence of disease recurrence or metastasis. Despite greater architectural complexity than WDPMT, MUMP has a similar bland cytology. It also has a low mitotic rate and Ki-67 nuclear labeling index, retention of MTAP and BAP1 expression, and benign clinical follow-up. If these cases were malignant mesotheliomas, one would have expected at least some of the patients to demonstrate disease recurrence or progression without adjuvant therapy within the follow-up time, particularly with limited resection in most patients. Therefore, the authors propose that mesothelioma of uncertain malignant potential be renamed complex mesothelial tumor of the tunica vaginalis. Using the term complex draws a contrast with the simple cuboidal lining and simple papillary architecture seen in WDPMT. In addition, labeling the lesion as a tumor removes the stigmata of uncertain malignant potential and mesothelioma, which can alarm patients and clinicians and potentially unduly lead to more extensive surgery in an attempt at “complete” resection. Furthermore, not definitively labeling the lesion as benign allows for the recommendation of clinical follow-up care.
Ding CC, Van Roo J, Kryvenko ON, et al. Mesothelioma of uncertain malignant potential (MUMP) of the tunica vaginalis: Proposal for reclassification as “complex mesothelial tumor of the tunica vaginalis.” Am J Surg Pathol. 2024;48(4):387–394.
Correspondence: Dr. J. I. Epstein at jonathaniraepstein@gmail.com
EBSA: a pattern of invasion linked to inferior outcomes in lung adenocarcinoma
The spread of lung adenocarcinoma cells into the bronchi and bronchioles is not well documented. The authors termed this histological finding endobronchial spreading of adenocarcinoma (EBSA) and investigated its prevalence and clinical significance. They reviewed 320 resected specimens from patients diagnosed with invasive adenocarcinoma. EBSA was observed in 144 (45 percent) patients. It was significantly associated with advanced pathological stage, higher histological grade, larger tumor invasion, lymphovascular infiltration, and spread through air spaces. Patients with EBSA had significantly shorter relapse-free and cancer-specific survival in univariate analysis (P<.001). In a subgroup analysis of patients with small-sized adenocarcinoma (invasion size, 30 mm or less) in the localized stage, EBSA was an independent inferior prognostic indicator in multivariate analysis. EBSA was observed in 11 patients in a subgroup analysis of patients with small-sized grade 1 nonmucinous adenocarcinoma (n=61). It was associated with significantly shorter relapse-free and cancer-specific survival (P=.026 and P=.001, respectively). The results demonstrated that EBSA is a significant risk factor for disease recurrence and cancer-related deaths. It can be considered a distinctive pattern of invasion and recognizing it can be beneficial to diagnosing lung adenocarcinoma.
Takahara T, Satou A, Tsuyuki T, et al. Endobronchial spread of adenocarcinoma is a distinct pattern of invasion and associated with inferior clinical outcomes in lung adenocarcinoma. Histopathology. 2024;84(4):646–660.
Correspondence: Dr. Taishi Takahara at ttakahara@aichi-med-u.ac
Study of TRPS1 as a highly sensitive marker for breast cancer
Trichorhinophalangeal syndrome 1 (TRPS1) is a nuclear protein highly expressed in breast epithelial cells. TRPS1 immunohistochemistry (IHC) has been suggested as a breast cancer marker. To determine the diagnostic and prognostic utility of TRPS1 IHC, the authors conducted a study in which they evaluated TRPS1 expression in 19,201 tumor samples from 152 tumor types and subtypes for which GATA3 data were available in a tissue microarray format. TRPS1 staining was seen in 86 of 152 tumor categories, with 36 containing at least one strongly positive case. TRPS1 staining predominated in various types of breast carcinomas (51 to 100 percent), soft tissue tumors (up to 100 percent), salivary gland tumors (up to 46 percent), squamous cell carcinomas (up to 35 percent), and gynecological cancers (up to 40 percent). TRPS1 positivity occurred in 1.8 percent of 1,083 urothelial neoplasms. In invasive breast carcinoma of no special type, low TRPS1 expression was linked to high grade (P=.0547), high pT (P<.0001), nodal metastasis (P=.0571), loss of estrogen receptor and progesterone receptor expression (P<.0001 each), and triple-negative status (P<.0001) but was unrelated to patient survival (P=.8016). In squamous cell carcinomas from 11 different sites, low TRPS1 expression was unrelated to tumor phenotype. Positivity for TRPS1 and GATA3 occurred in 47.4 to 100 percent of breast cancers, up to 30 percent of salivary gland tumors, and 0.3 percent of 9,835 tumors from 134 other cancer entities. TRPS1 IHC has high utility for identifying cancers of breast or salivary gland origin, especially in combination with GATA3. The virtual absence of TRPS1 positivity in urothelial neoplasms is useful for distinguishing GATA3-positive urothelial carcinoma from breast cancer.
Lennartz M, Löhr N, Höflmayer D, et al. TRPS1 is a highly sensitive marker for breast cancer: A tissue microarray study evaluating more than 19,000 tumors from 152 different entities. Am J Surg Pathol. 2024;48(6):637–651.
Correspondence: Dr. Ronald Simon at r.simon@uke.de