Intra-thoracic desmoid tumor

Abstract

Desmoid tumor is a rare, benign soft tissue tumor having potential for local invasion. It commonly arises in abdominal wall, presenting as a palpable mass. We describe a case of thoracic desmoid tumor in a middle aged male arising from the chest wall. Unlike the usual presentation, two separate non-palpable tumor masses protruded into left thoracic cavity mimicking lung carcinoma. The patient underwent successful complete surgical excision of the tumor. Such tumors, being rare, may pose diagnostic problems if not considered in the initial work up.

INTRODUCTION

Desmoid tumor, also known as aggressive fibromatosis, account for only 0.03% of all neoplasms.[1] It arises from fascia and connective tissue of the muscular layers. About 50% of the tumors arise in the abdominal region[2] while chest wall involvement is seen in very few cases,[3] usually presenting as a palpable mass. Multiple, impalpable, intrathoracic desmoid tumors is a rare presentation. We could not find a case with similar presentation in the scientific literature.

CASE REPORT

A 50-year-male presented in OPD with complaints of chest pain over left mammary and axillary area. Pain was present since 3 years, was slowly progressive, and not related to respiratory movements. Patient was smoker and had lost approximately 5 kg of weight in last 6 months. There was no past history of trauma. Physical examination was unremarkable except for dull note on percussion and decreased breath sounds in left mammary and axillary area. His hemogram and liver function tests were within normal limits. Multiple sputum samples for acid fast bacilli and cytology were inconclusive. An X-ray chest showed a well defined opacity involving left upper and mid zones, abutting the chest wall [Figure 1a]. Computed tomography (CT) scan thorax revealed a homogenous soft tissue density mass lesion in the left hemithorax along with evidence of local invasion of adjoining ribs [Figure 1b]. The mass was broad based and projecting into the thorax. Fine needle aspiration cytology of the mass diagnosed it to be spindle cell tumor of the pleura. Post procedure, patient developed ipsilateral pneumothorax, which indirectly confirmed the chest wall origin of the growth. Later, patient underwent left antero-lateral thoracotomy, which revealed two separate masses lying adjacent to each other and adherent to 4^th, 5^th, and 6^th ribs. Wide local excision of the tumor masses along with affected ribs was done. The resected masses were 10 × 12 cm [Figure 2a] and 4 × 6 cm in dimensions, respectively. Histopathology revealed circumscribed tumor composed of spindle cells with bland nuclei and abundant extracellular collagen in the stroma [Figure 2b]. The lesion was typical of fibromatosis (desmoid tumor). Post-operative X-ray showed complete resolution of the shadow [Figure 3]. Patient had uneventful recovery and was discharged on 13^th post-operative day.

Figure 1.

(a): X-ray chest P-A view showing well defined opacity in the left hemithorax (upper and mid zones) abutting the chest wall. (b) CT scan thorax (section just below carina) showing a mass protruding into the left hemithorax and eroding the adjoining ribs

Figure 2.

(a) Excised tumor mass with its cut surface. (b) Histopathology section showing spindle cells with bland nuclei and abundant extracellular collagen in the stroma (H and E, ×200)

Figure 3.

Post-operative X-ray chest after removal of the tumor and 4^th, 5^th, and 6^th ribs

DISCUSSION

Desmoid tumor is an aggressive form of fibromatosis of musculoaponeurotic origin. It is a histologically benign, slow growing tumor commonly presenting in the age group of 15-60 years. Apart from abdominal sites, it may also arise from the chest wall,[3] shoulder, foot, thigh, or calf.[4] Despite being indolent in nature it has characteristic tendency for local infiltration causing pressure effects on surrounding organs.

The etiology of tumor is not well defined. History of prior trauma is found in 25% of patients.[2] The tumor has also been found to be associated with a condition called familial adenomatous polyposis (FAP)[5,6] with increased risk of developing desmoid tumor in such patients. A number of reports have also documented increased incidence of desmoid tumor in women of reproductive age and its therapeutic response to anti-estrogen therapy suggesting the role of estrogens in tumor causation.[7]

Desmoid tumor usually presents as painless palpable mass but, less commonly, may project inwards and is detectable only on imaging.[8] Pain may occur due to nerve involvement giving rise to sensory and motor symptoms in the distribution of the nerve.[8]

Definitive diagnosis of desmoid requires histopathological examination. Fine needle aspiration may not be useful due to hypocellularity of the tumor.[3] Intrathoracically located desmoid may sometimes pose a diagnostic dilemma. Important differentials to be looked for in such cases include neurofibromas, fibrosarcomas, mesothelioma, ganglioneuromas, lung cancers, calcifying fibrous pseudotumors, and localized fibrous tumors of the pleura.[9] Complete surgical excision with wide tumor-free margins is the treatment of choice. Despite complete excision, chest wall desmoid is known for its high rate of recurrence,[6] though exact rate is not known in view of its rarity. In one recent published series of chest wall desmoid tumors, 5-year survival rate was found to be 93%, while 5-year local recurrence rate was 29%.[10] These findings strengthens the fact that continued vigilance is required in every operated case even if wide tumor-free surgical margins have been attained. Re-excision is usually suited for such recurrent tumors. Few published data and reports have also advocated function and structure preserving surgery instead of wide local excision, in order to prevent unnecessary morbidity. Other treatment modalities being used singly or in combination include chemotherapy,[11] radiation therapy,[12] hormonal therapy, non-steroidal anti-inflammatory drugs,[13] and anti-allergic drug like tranilast.[14]

In the present patient, the thoracic location of the tumor, pattern of growth (protruding into the thoracic cavity) as well as its presentation (2 separate tumor masses lying adjacent to each other) made the case rare and unusual. To conclude, the present case demonstrates complexities involved in the presentation and management of these rare tumors and highlight the need to be vigilant while managing patients with thoracic masses.