pleural mesothelioma is a rare condition associated with exposure to asbestos in around 70% of the cases .
other risk factors include sv40 virus , genetic alterations , and exposure to radiotherapy generally for cancer treatment .
the relationship between exposure to radiotherapy and pleural mesothelioma has been documented in the literature . also , metastatic skeletal involvement is common in carcinoma breast .
follow - up tc- methylene diphosphonate ( mdp ) bone scintigraphy ( bs ) helps in early detection of skeletal metastases especially in high - risk patients . here , we present the case of 50-year - old female of carcinoma left breast treated with modified radical mastectomy , followed by radiotherapy who underwent bs on follow - up which was negative for the skeletal metastases but showed abnormally increased left rib cage uptake that led to the incidental detection of malignant pleural mesothelioma .
a 50-year - old female patient of carcinoma left breast underwent modified radical mastectomy , followed by radiotherapy 12 years back .
suspecting the pain to be of musculoskeletal origin , the treating oncologist referred the patient for tc - mdp bs to rule out skeletal metastases .
bs was done 3 h , following intravenous injection of 20 mci of tc - mdp .
it revealed diffusely increased radiotracer uptake involving all the left - sided ribs thus giving the appearance of asymmetrically increased left rib cage uptake [ figure 1a and b ; arrows ] .
the remaining skeleton showed normal radiotracer distribution . because this pattern was atypical for rib metastasis , single photon emission computed tomography / computed tomography ( spect / ct ) of the thorax was done in the same setting .
transaxial spect and spect / ct images [ figure 1c and e ; arrows ] revealed diffusely increased radiotracer uptake in all the left - sided ribs . using bone window on ct [ figure 1d ] , all the left - sided ribs showed regular cortical outlines with no apparent abnormality .
transaxial ct in soft tissue window revealed circumferential nodular left - sided pleural thickening [ figure 1f ; arrow , arrow head ] .
the increased uptake of tracer in the ribs was likely secondary to the increased vascularity in underlying pleural pathology and was interpreted as reactive in nature .
biopsy from the pleural - based nodular lesion was suggestive of pleural mesothelioma [ figure 2a - d ] .
99mtc - methylene diphosphonate bone scintigraphy showing diffusely increased left rib cage uptake ( anterior a , posterior b ; arrows ) .
transaxial single photon emission computed tomography ( spect ) and spect / ct images ( c , e ; arrows ) show diffusely increased radiotracer uptake involving the left - sided ribs .
transaxial ct ( bone window , d ) shows normal left - sided ribs with regular cortical outlines .
transaxial ct ( soft tissue window , f ) shows a pleural - based soft tissue density lesion in the left lung lower lobe ( f , arrow head ) with diffuse circumferential pleural thickening ( f , arrow ) histological evaluation ( 4 , a ; 10 , b ; 20 , c ) shows hematoxylin - and eosin - stained sections showing round to oval cell with moderate amount of cytoplasm with mild nuclear pleomorphism .
during the course of their disease , about one third of patients with breast cancer are at risk of developing recurrence .
therefore , early diagnosis and treatment of recurrent breast cancer is important to define therapeutic strategies to enhance the duration of survival .
metastatic skeletal involvement is common in patients with breast cancer and has been demonstrated by postmortem studies in up to 70% of the patients .
detection of these lesions has a prognostic as well as therapeutic significance as the mean survival in patients with bony metastases is only 2 years .
rib involvement is common in patients with multiple metastases but an uncommon site for solitary metastases .
malignant pulmonary and pleural disease usually heralds poor prognosis , the manifestation of which can be either solid disease or a malignant pleural effusion , or a combination of both .
ct is the workhorse of pleural imaging , able to achieve specificity of close to 100% .
the latency period for developing pleural mesotheliomas may vary depending upon the type of etiology .
our extensive literature search revealed few cases of carcinoma breast who later on developed pleural mesothelioma attributed to radiotherapy given for the treatment of breast cancer . in patients of carcinoma breast treated with radiotherapy , the time interval between the radiation and the appearance of the mesothelioma ranges from 10 to 30 years .
this is in contrast to asbestos - related mesotheliomas , where there is a greater time interval ( usually 30 - 40 years ) and patients are also much older ( usually > 60 years ) . in the present study ,
therefore , we hypothesized that radiotherapy given for the treatment of primary breast cancer could have played a role in the development of pleural mesothelioma .
although there was no evidence of skeletal metastasis , the demonstration of pleural pathology by spect / ct played an important role in the patient management as timely treatment increases the survival of the patients .
therefore , this pattern of asymmetrical hemithoracic rib cage uptake on bs should be kept in mind as an indirect indicator of underlying pleural involvement warranting further investigation for documenting the same .
 follow - up bone scintigraphy ( bs ) in a patient of carcinoma left breast , who was treated with surgery followed by radiotherapy 12 years back , revealed asymmetrically increased radiotracer uptake in left - sided ribs . since , this pattern was atypical for metastatic rib involvement , single photon emission computed tomography / computed tomography ( spect / ct ) of thorax was done in the same setting which revealed circumferential nodular left - sided pleural thickening . 
 biopsy confirmed it to be pleural mesothelioma . 
 left - sided ribs showed no abnormality on ct , thus suggesting the rib uptake as reactive in nature . 
 this pattern of asymmetric rib uptake on bs should be kept in mind and warrants further investigation for determining underlying pathology . 
INTRODUCTION
CASE REPORT
DISCUSSION