Pleural malignant mesothelioma with invasive micropapillary component and its association with pulmonary metastasis

Abstract

The micropapillary pattern (characterized by papillary structure with tufts lacking a central fibrovascular core) is a predictor of aggressive carcinoma. The purpose of the present study was to review 34 pleural malignant mesotheliomas (21 epithelioid, five sarcomatoid, seven biphasic and one lymphohistiocytoid), with special reference to the presence of invasive micropapillary component. Two invasive micropapillary pattern-positive tumors were identified. The invasive micropapillary pattern was seen to have a focal distribution in 15-20% of the tumor tissues. The majority of the invasive micropapillary clusters expressed MUC1 along the outer cell surface. Analysis of pleural malignant mesotheliomas with epithelioid features and with or without invasive micropapillary pattern (21 epithelioid and seven biphasic subtypes) indicated pulmonary micrometastases in only the invasive micropapillary-positive tumors (P < 0.015), and the spread was probably via the lymphatics. Lymphatic involvement (confirmed on immunohistochemistry with D2-40 antibody) and lymph node metastasis were found in both of the invasive micropapillary-positive tumor patients, whereas they were noted in only one of 10 (10%, P < 0.046) and three of nine (30%) invasive micropapillary-negative patients. To the authors' knowledge this is the first study to indicate the presence of invasive micropapillary component in pleural malignant mesothelioma. This component can predict more aggressive lymphatic spread, similar to that of carcinomas in other organs with micropapillary pattern.

Pleomorphic Epithelioid Diffuse Malignant Pleural Mesothelioma: A Clinicopathological Review and Conceptual Proposal to Reclassify as Biphasic or Sarcomatoid Mesothelioma

“…It is rarely reported in DMPM. 21,36 Mogi et al 21 reported a micropapillary component in 2 of 34 DMPM (5.9%), and these cases showed significantly more lymphatic invasion, pulmonary metastasis, and a trend toward more lymph node involvement compared with those without a micropapillary component. In our series, 20 cases (9%) out of 232 patients with epithelioid DMPM were micropapillary predominant.…”

“…The micropapillary pattern was defined as papillary structures with tufts lacking a central fibrovascular core (Figure 1C). 11,21 The solid pattern consists of sheets or nests of polygonal to round tumor cells, lacking any specific morphologic arrangement or pleomorphism (Figure 1D). 1,6 Tumors with anaplastic or prominent giant cells were designated as pleomorphic features (Figure 1E).…”

A Rare Case of Mesothelioma Showing Micropapillary and Small Cell Differentiation with Aggressive Behavior

“…However, clinical, radiological, histological, and ultrastructural features along with D2-40, HBME-1, and WT-1 expression were definitive for a diagnosis of mesothelioma. A micropapillary pattern in mesothelioma has been rarely reported [ 2 ], but, when present, this growth pattern shows poor prognosis with aggressive lymphatic invasion and lymph node metastasis. In a previous study of small cell mesothelioma, tumor cells showed immunoreactivity for neuron-specific enolase and cytokeratin, but not for chromogranin A and CEA [ 3 ].…”

“…Pleural mesothelioma is a rare neoplasm and roughly 70% are the epithelioid type, which is characterized by proliferation of epithelioid tumor cells with a tubulopapillary growth pattern [ 1 ]. There have been few reports of mesothelioma having a micropapillary pattern [ 2 ] and a small cell component [ 3 ]. To the best of our knowledge, there has been no previously reported case containing both micropapillary and small cell components.…”

Guidelines for Pathologic Diagnosis of Malignant Mesothelioma 2017 Update of the Consensus Statement From the International Mesothelioma Interest Group

“…31 Of note, a micropapillary pattern (without central fibrovascular core) should be classified as something other than tubulopapillary because a micropapillary pattern correlates with a higher incidence of lymphatic invasion. 32 In addition, tubulopapillary epithelioid mesotheliomas require distinction from well-differentiated papillary mesotheliomas (WDPMs), which are classified as a separate subtype in the 2015 World Health Organization classification, 24 although WDPMs can (rarely) show invasive foci. 33 Recently, epithelioid mesotheliomas with marked nuclear pleomorphism in more than 10% of the tumor have been shown to behave like sarcomatoid and biphasic variants, with a proposal that a ''pleomorphic'' MM variant be recognized as an adversely prognostic epithelioid pattern.…”