J Pathol Transl Med.  2018 Jul;52(4):219-225. 10.4132/jptm.2018.05.16.

Endobronchial Smooth Muscle Tumors: A Series of Five Cases Highlighting Pitfalls in Diagnosis

• Nakra T
• Kakkar A
• Agarwal S
• Madan K
• Sharma SC
• Jain D

• KMID: 2417805
• DOI: http://doi.org/10.4132/jptm.2018.05.16

Abstract

BACKGROUND
Primary endobronchial smooth muscle tumors (SMTs), which are extremely rare, include endobronchial leiomyomas and leiomyosarcomas. Clinically, SMTs present with signs and symptoms of bronchial obstruction, and lack specific radiological findings. Thus, histopathological examination is required for accurate diagnosis as well as for tumor grading. We examined the histomorphological and immunohistochemical features of endobronchial SMTs and highlighted pitfalls in diagnosis, particularly when using small biopsies.
METHODS
Cases of primary endobronchial SMTs diagnosed at our Institute over the last 6 years (2012-2017) were retrieved from the departmental archives. Histopathological features and immunohistochemistry performed for establishing the diagnosis were reviewed.
RESULTS
Five cases of SMTs occurring in endobronchial locations were identified. These included three cases of leiomyoma, and two cases of leiomyosarcoma. The age distribution of patients ranged from 13 to 65 years. Leiomyomas showed more consistent staining with smooth muscle markers (smooth muscle actin, desmin, and smooth muscle myosin heavy chain), while tumors of higher grade showed variable, focal staining, leading to erroneous diagnosis, especially on small biopsies.
CONCLUSIONS
The diagnosis of endobronchial SMTs relies on histopathological examination, for both confirmation of smooth muscle lineage and determination of the malignant potential of the lesion. Appropriate immunohistochemical panels including more than one marker of smooth muscle differentiation are extremely valuable for differential diagnosis from morphological mimics, which is necessary for instituting appropriate management.

Keyword

Endobronchial; Leiomyoma; Leiomyosarcoma; Smooth muscle tumor; Immunohistochemistry

MeSH Terms

Actins
Age Distribution
Biopsy
Desmin
Diagnosis*
Diagnosis, Differential
Humans
Immunohistochemistry
Leiomyoma
Leiomyosarcoma
Muscle, Smooth*
Myosins
Neoplasm Grading
Smooth Muscle Tumor*
Actins
Desmin
Myosins

Figure

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  Fig. 1. Clinical and radiological features in patient 1. (A) Flexible bronchoscopic image showing an endoluminal mass in the right main bronchus. (B) Coronal computed tomography reconstructed image showing a mass lesion in the right main bronchus (case 1).

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  Fig. 2. Leiomyoma. (A) Photomicrographs of case 3 show bronchial epithelium with a sub-epithelial spindle cell tumor arranged in fascicles. (B) Tumor cells have abundant cytoplasm and ovoid nuclei with homogeneous chromatin. (C, D) Areas of hyalinization and calcification are noted in case 2. Immunohistochemistry shows diffuse smooth muscle actin (E) and desmin positivity (F).

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  Fig. 3. Leiomyosarcoma. (A, B)Photomicrographs of the first biopsy from case 4 show small fragments of spindle cell tumor with mild to moderate nuclear pleomorphism and interspersed inflammatory cells; diagnosed as inflammatory myofibroblastic tumor. (C) Excision biopsy showed bronchial epithelium with a cellular spindle cell tumor in the sub-epithelial region. (D) Tumor cells have pale to bright eosinophilic cytoplasm, paranuclear vacuoles (black arrow) with interspersed inflammatory cells and pleomorphic tumor giant cells (red arrow). Immunohistochemistry shows focal positivity for smooth muscle actin (E) and desmin (F).

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  Fig. 4. Leiomyosarcoma. Photomicrographs of case 5 show multiple fragments of tumor tissue displaying a cellular spindle cell tumor (A) with moderate amounts of eosinophilic cytoplasm, ovoid, hyperchromatic nuclei, paranuclear vacuoles, and mitotic figures (B); perivascular hyalinization is noted (C). (D) Immunohistochemistry shows focal desmin positivity.

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