WBR0862

Author	[[PageAuthor::Serge Korjian M.D. (Reviewed by Serge Korjian)]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Pathology
Sub Category	SubCategory::Pulmonology
Prompt	[[Prompt::A 56-year-old man presents to the neurology clinic for 3 weeks of upper and lower extremity weakness. The patient explains that he works as a plumber and that his everyday chores have become much harder since he has started to notice this weakness. Despite this, he has noticed a pattern that allows him to overcome it. He reports that the longer he is at rest, the weaker he feels, and as soon as he exerts himself he restores a lot of the strength in his extremities. Physical exam reveals 2/5 strength in all four extremities, bilateral eyelid ptosis, and absent deep tendon reflexes. With a certain diagnostic suspicion, the physician orders a chest CT that reveals a 2.5 cm mass adjacent to the left stem bronchus. Biopsy of the mass is likely to reveal which of the following findings?]]
Answer A	AnswerA::Small dark blue neuroendocrine cells
Answer A Explanation	AnswerAExp::This pattern is typical of SCLC.
Answer B	AnswerB::Keratin pearls and retracted cells
Answer B Explanation	AnswerBExp::This pattern is seen in squamous cell carcinoma. Paraneoplastic syndromes associated with squamous cell carcinoma include PTHrP hypercalcemia.
Answer C	AnswerC::Pleomorphic giant cells
Answer C Explanation	AnswerCExp::This pattern is typical of large cell lung carcinoma.
Answer D	AnswerD::Granuloma formation with caseating necrosis
Answer D Explanation	AnswerDExp::This pattern is usually diagnostic of active tubeculosis.
Answer E	AnswerE::Granuloma formation without caseating necrosis
Answer E Explanation	AnswerEExp::This pattern is usually seen in sarcoidosis and some cases of tuberculosis.
Right Answer	RightAnswer::A
Explanation	[[Explanation::Lambert Eaton myasthenic syndrome (LEMS) is a neuromuscular autoimmune disease often presenting in the context of a paraneoplastic syndrome associated with small cell lung cancer. Patients typically present with weakness of the proximal extremities manifesting as difficulty raising arms and rising from a chair. Other symptoms may include diplopia, ptosis, dysphagia and autonomic dysfunction. Small cell lung cancer (SCLC) is an undifferentiated neoplasm and so far the deadliest cancer in men and women. SCLC is known to be associated with paraneoplastic syndromes including ectopic horomone secretion (ACTH and ADH) as well as LEMS. On pathology, SCLC appears as undifferentiated small blue cells that loosely resemble neuroendocrine cells given their origin. these cells are referred to as Kulchitsky cells. SCLC is usually inoperable and responds to chemotherapeutic regimens to different extents. A pathology specimen of SCLC can be seen below. Educational Objective: SCLC is an undifferentiated lung tumor that appears as small dark blue cells known as Kulchitsky cells. SCLC is associated with many paraneoplastic syndromes namely LEMS. References: Titulaer MJ, Lang B, Verschuuren JJ. Lambert–Eaton myasthenic syndrome: from clinical characteristics to therapeutic strategies. The Lancet Neurology. 2011;10(12):1098-1107. van Meerbeeck JP, Fennell DA, De Ruysscher DK. Small-cell lung cancer. The Lancet. 2011;378(9804):1741-1755. Image attribution: Nephron. 2010. Licensed under the Creative Commons Attribution-Share Alike 3.0 license.]]
Approved	Approved::Yes
Keyword	WBRKeyword::Kulchitsky cells, WBRKeyword::Small cell lung carcinoma, WBRKeyword::Lambert Eaton Myasthenic Syndrome, WBRKeyword::LEMS, WBRKeyword::Paraneoplastic, WBRKeyword::lung cancer, WBRKeyword::myasthenia gravis
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