Pulmonary sarcomatoid carcinoma presenting as a necrotizing cavitary lung lesion: diagnostic dilemma

Discussion

PSC is a rare variant of non-small-cell carcinoma lung cancer, accounting for up to 0.4% of lung malignancy.¹ It was recently subtyped by the World Health Organization as a non-small cell lung carcinoma with certain amount of differentiation resembling sarcoma or containing elements of sarcoma.^2-4 It is not known why both elements co-exist in the tumor, but Franks and colleagues some theories have been postulated in the literature, including possible origin from a single, aberrant stem cell with progenies differentiating in two separate pathways.³

Sarcomatoid carcinoma consists of spectrum of tumors including pleomorphic carcinoma, spindle cell carcinoma, giant cell carcinoma, carcinosarcoma, and blastoma.^3,4 It usually shows male preponderance, and association with smoking.³ The diagnosis commonly occurs in the sixth decade of life, except for pulmonary blastoma, which is more common in the fourth decade and with equal gender distribution.⁴

The presenting symptoms can be variable and nonspecific, but predominantly include chest pain, cough, hemoptysis, and/or weight loss.⁵ Radiologically, pulmonary sarcomatoid cancer presenting as a necrotizing cavitary lesion in the lung is a rare finding, seldom reported in the past.^6,7 The presentation in our case, with necrotizing lymphadenitis, was reminiscent of an infectious or autoimmune etiology such as tuberculosis or granulomatosis with polyangiitis. The presence of extensive necrosis in the lesion and the characteristic heterogeneity of the tumor had resulted in inconclusive biopsy findings during the previous presentation. In clinical practice, there is over-reliance on biopsy findings to make the distinction between cancer and other mimicking conditions. This is especially true for rare tumors such as PSC, which often results in misdiagnosis and a delay in administering the proper treatment.

Transbronchial biopsy in cases such as the present case, carries little benefit because the diagnosis depends on the site from which the biopsy is taken and whether the biopsied tissue is representative of the entire mass. The diagnosis can be suspected based on the clinical and radiological findings but confirmation requires a surgical resection to delineate the accurate cytology and architecture.^5,6,8 Huang and colleagues showed a misdiagnosis rate of PSC of >70% preoperatively.⁴ Resective surgery is feasible only in patients with high index of suspicion for a malignancy, which in most cases requires previous confirmation with a biopsy. The rarity of this cancer, its unusual presentations, and the lack of specific testing preclude early diagnosis and timely treatment of this fatal condition.

Initial treatment options for localized or with limited spread disease is resective surgery. The role of chemo- or radiation therapy is not known, but they have not previously shown promising results,^6,8 except in some cases when they are used as postoperative adjuvant chemotherapy⁴ or in bulky, locally invasive tumors.¹ The recurrence rate after surgery is very high, resulting in a poor 5-year survival rate.^1,8 Experimental therapies, such as antibodies that target epidermal growth factor receptor mutations, have not shown much success either.⁸ In conclusion, the outlook for patients with PSC with the current available knowledge and treatment protocols, is dismal.

Most of the current knowledge and data in the literature is based on cases from autopsy or early-stage surgical resections rather than on patients with advanced cancer.⁵ Moreover, the role of surgical resection in PSC is questionable, given the high recurrence rate. Subsequently, the clinical and pathological manifestations have yet to be well characterized.⁴ There has been advance with the publication of more studies recently. Cytokeratin markers such as CAM 5.2 and AE1/AE3 are commonly useful to support the diagnosis when suspected.³ Other markers, including the carcinoembryonic antigen, CD15, and thyroid transcription factor-1 may be variably positive, based on the differentiation of the cancer. Other exciting prospects in the study of PSC include the suggestion of a modified vimentin histologic score for better characterization of the cancer and the discovery of high platelet-derived growth factor receptor beta immunohistochemistry expression in PSC as a potential target for future therapy.

Conclusion

Pulmonary sarcomatoid lung cancer can present with a predominant necrotizing picture that mimics diseases such as tuberculosis. In such case, transbronchial biopsy carries little benefit because the diagnosis depends on whether the biopsied tissue is representative of the entire mass, often confounded by the extensive necrosis. More data is needed to determine prognostic factors and appropriate therapeutic strategies.